The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > Heavy Haulers

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 05-29-2016, 10:55 PM   #1
5Tractorguy
Registered User
 
5Tractorguy's Avatar
 
Join Date: May 2015
Location: Central Massachusetts
Posts: 494
Gear ratio speed question

Got a quick gear ratio question.

I have a '61 GMC 5000 with a NP540 trans (direct drive in 5th) and split rear. 9.00-20 tires. Right now I top out at 35-40ishmph, 30mph cruising comfortably. My gears in the differential are 6.50HI and 9.04LOW.

Is this speed about right for what I have in my truck? Anyone have one similar? I realize it's old and all but it would be great to get at least 45mph, but I think that's going to take some serious gear changing to do.

Any help would be appreciated....
__________________
Jake

5Tractorguy on Youtube
5Tractorguy is offline   Reply With Quote
Old 06-04-2016, 11:59 PM   #2
mrolds88
Registered User
 
Join Date: Jul 2011
Location: WV
Posts: 946
Re: Gear ratio speed question

Jake, check your 2 speed. Sounds like it's in low range.
__________________
72 GMC C2500 402/Th400 first truck (still have)
77 GMC C3500 CC dually Sold
70 C50 dump truck "Rusty"
87 K10 Suburban Sold
93 K2500 xcab 6.5TD
96 GMC K2500 Suburban 6.5 TD
mrolds88 is offline   Reply With Quote
Old 06-05-2016, 09:29 PM   #3
5Tractorguy
Registered User
 
5Tractorguy's Avatar
 
Join Date: May 2015
Location: Central Massachusetts
Posts: 494
Re: Gear ratio speed question

Quote:
Originally Posted by mrolds88 View Post
Jake, check your 2 speed. Sounds like it's in low range.
Will do 88. I'll check back mid-week. Going to bring it to the house Wednesday (storing it at uncles place).
__________________
Jake

5Tractorguy on Youtube
5Tractorguy is offline   Reply With Quote
Old 06-06-2016, 09:49 AM   #4
greywuuf
Registered User
 
Join Date: Jul 2007
Location: Alaska
Posts: 516
Re: Gear ratio speed question

I would have to agree....I have a '75. 7500 (two of them actually) with 9.00x20's and 5 speeds... .One with the 6.xx or 8.xx two speed one with and undetermined single speed axle and the top out around 48- 50 mph .....Though both of mine are Detroit powered and tact out at 2800....slower than that would almost HAVE to be either "low range" or truely "deep" rear end gearing.
greywuuf is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 04:15 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com